Czapek Dox Agar modified by Oxoid (CDA) suppressed significantly the growth of Sclerophoma pythiophila (Gda.) Hohn compared to that on either of Malt Extract Agar, Potato Dextrose Agar or Oat Meal Agar. The effects of the individual ingredient of CDA on the growth of the fungi were also assessed. It was found that magnesium glycerophosphate of CDA was toxic to S. pythiophila but not to Ramichloridium pini de Hoog and Rahman. An increase of the dose of this salt from 0.5 to 4.0 g/1 of CDA medium resulted a further significant suppression of S. pythiophila compared to the growth of the fungus on CDA and supported considerably higher
growth of R. pini upto ten days. The new modified GDA medium was effective to act as a medium for selective isolation of R. pini and suppression S. pythiophila.